Numerous attempts have been made to increase the emission intensity of light emitting diodes. It has thus been proposed to arrange a plurality of very small light emitting diode semiconductor chips closely adjacent to one another in order to attain a higher luminous efficiency. A problem in this case, of course, is the heat dissipation, since the closely adjacent arrangement of the semiconductor chips means that the latter become very hot at corresponding power.
It has therefore been attempted to separate the light emission from the thermal radiation if possible and to cause the thermal radiation to be radiated principally toward the rear and, by contrast, the light emission toward the front.
Such considerations also give rise to the so-called flip-chip technique, which involves fitting one or a plurality of semiconductor chips onto a light-transmissive substrate, which may be made of sapphire or the like, by way of example.
A reflector layer, for example made of silver, extends on that side of the chip or chips which is remote from the sapphire, both the contact-connection and the heat dissipation being effected by means of very thick posts, so-called bumps, which make contact with the chip in a suitable manner.
In the case of this solution, the intention is then for as much heat as possible to be dissipated toward the rear if possible, while light, amplified by the silver reflection layer, is intended to leave the light emission device through the sapphire substrate toward the front.
Endeavors have also been made for a relatively long time to increase the optical efficiency of light emission devices. For this purpose, combinations of converging lenses and reflectors are usually used, which concentrate the emitted light and are intended to reduce the generation of spurious light and scattered light.
It has recently been proposed, for example, in accordance with German Patent Application 10 2006 015 377 to form a semiconductor radiation source with a plurality of LED chips which are contact-connected by means of a printed circuit board brought up close, wherein a reflector in combination with a converging lens is intended to ensure a highest possible luminous efficiency, but the generated heat is nevertheless intended to be dissipated well.
Although a semiconductor radiation source of this type is basically already highly suitable if it is necessary to ensure a highest possible luminous efficiency, it would be desirable, however, to improve the luminous efficiency even further without increasing the emission of heat.